Stationary Lifshitz black holes of R^2-corrected gravity theory

In this short note, I present a generalization of a set of static D-dimensional (D >= 3) Lifshitz black holes, which are solutions of the gravitational model obtained by amending the cosmological Einstein theory with the addition of only the curvature-scalar-squared term and that are described by two parameters, to a more general class of exact, analytic solutions that involves an additional parameter which now renders them stationary. In the special D=3 and the dynamical exponent z=1 case, the parameters can be adjusted so that the solution becomes identical to the celebrated BTZ black hole metric.Comment: 7 pages, no figures; ver. 2: added 5 new references (accepted by PRD as a Brief Report

Hamiltonian Electric/Magnetic Duality and Lorentz Invariance

In (3+1) Hamiltonian form, the conditions for the electric/magnetic invariance of generic self-interacting gauge vector actions and the definition of the duality generator are obvious. Instead, (3+1) actions are not intrinsically Lorentz invariant. Imposing the Dirac-Schwinger stress tensor commutator requirement to enforce the latter yields a differential constraint on the Hamiltonian which translates into the usual Lagrangian form of the duality invariance condition obeyed by Maxwell and Born-Infeld theories. We also discuss covariance properties of some analogous scalar models.Comment: 7 pages, LaTeX, no figure

Shock-Free Wave Propagation in Gauge Theories

We present the shock-free wave propagation requirements for massless fields. First, we briefly argue how the "completely exceptional" approach, originally developed to study the characteristics of hyperbolic systems in 1+1 dimensions, can be generalized to higher dimensions and used to describe propagation without emerging shocks, with characteristic flow remaining parallel along the waves. We then study the resulting requirements for scalar, vector, vector-scalar and gravity models and characterize physically acceptable actions in each case.Comment: 30 pages, LaTeX, no figure

Supersymmetric Strings and Waves in D=3, N=2 Matter Coupled Gauged Supergravities

We construct new 1/2 supersymmetric solutions in D=3, N=2, matter coupled, U(1) gauged supergravities and study some of their properties. In the most general case they represent a string superposed with gravitational and Chern-Simons electromagnetic waves. The waves are attached to the string and the solution satisfies an electromagnetic self-duality relation. When the sigma model is non-compact it interpolates between an asymptotically Kaigorodov space and a naked singularity. For the compact sigma model there is a regular horizon with the Kaigorodov geometry and asymptotically it is either Minkowskian or a pp-wave. When the sigma manifold is flat our solutions describe either AdS_3 or Kaigorodov space or a pp-wave in AdS_3.Comment: 19 pages, 1 figure, v2:a reference added, minor improvement

Godel-Type Metrics in Various Dimensions

Godel-type metrics are introduced and used in producing charged dust solutions in various dimensions. The key ingredient is a (D-1)-dimensional Riemannian geometry which is then employed in constructing solutions to the Einstein-Maxwell field equations with a dust distribution in D dimensions. The only essential field equation in the procedure turns out to be the source-free Maxwell's equation in the relevant background. Similarly the geodesics of this type of metric are described by the Lorentz force equation for a charged particle in the lower dimensional geometry. It is explicitly shown with several examples that Godel-type metrics can be used in obtaining exact solutions to various supergravity theories and in constructing spacetimes that contain both closed timelike and closed null curves and that contain neither of these. Among the solutions that can be established using non-flat backgrounds, such as the Tangherlini metrics in (D-1)-dimensions, there exists a class which can be interpreted as describing black-hole-type objects in a Godel-like universe.Comment: REVTeX4, 19 pp., no figures, improved and shortened version, note the slight change in the title [accepted for publication in Classical and Quantum Gravity

Negative Mass Solitons in Gravity

We first reconstruct the conserved (Abbott-Deser) charges in the spin connection formalism of gravity for asymptotically (Anti)-de Sitter spaces, and then compute the masses of the AdS soliton and the recently found Eguchi-Hanson solitons in generic odd dimensions, unlike the previous result obtained for only five dimensions. These solutions have negative masses compared to the global AdS or AdS/Z_p spacetimes. As a separate note, we also compute the masses of the recent even dimensional Taub-NUT-Reissner-Nordstrom metrics.Comment: 12 pages, RevTEX4; typos fixed; v3: version to appear in PRD, references adde

On The Supersymmetric Solutions of D=3 Half-maximal Supergravities

We initiate a systematic study of the solutions of three-dimensional matter-coupled half-maximal (N=8) supergravities which admit a Killing spinor. To this end we analyze in detail the invariant tensors built from spinor bilinears, a technique originally developed and applied in higher dimensions. This reveals an intriguing interplay with the scalar target space geometry SO(8,n)/(SO(8) x SO(n)). Another interesting feature of the three-dimensional case is the implementation of the duality between vector and scalar fields in this framework. For the ungauged theory with timelike Killing vector, we explicitly determine the scalar current and show that its integrability relation reduces to a covariant holomorphicity equation, for which we present a number of explicit solutions. For the case of a null Killing vector, we give the most general solution which is of pp-wave type.Comment: 29 page